Public concern over the oceans typically focuses on oil spills and the fouling of beaches, but far greater threats are posed by coastal habitat destruction, overfishing, and pollution from industry, farms and households that daily drains into the sea, concludes the author in Abandoned Seas: Reversing the Decline of Oceans. These assaults imperil not only fish--an important source of protein for much of the world--but the diversity of marine life and even the global climate.

The world's oceans, the leading source of animal protein in the human diet, are showing marked signs of deterioration, according to Peter Weber, author of the study. The United Nations' Food and Agriculture Organization estimates that all 17 of the world's major fishing areas have either reached or exceeded their natural limits. Nine of these fisheries are in serious decline.

The destruction of thousands of miles of coastal habitats is a visible measure of the decreased health of the oceans. Some two thirds of all oceanic fish caught for human consumption spend the early stages of life in the rapidly disappearing ecosystems where oceans meet land. Much of these fragile, rich breeding and feeding grounds have been destroyed to make room for cities, harbors and shrimp farms. The more that human population growth and urban development intrude into coastal areas, the more the fish catch will likely decline.

Failing oceans affect far more than food supply. They also threaten the "biological pump"--the mechanism by which marine photosynthesis absorbs carbon dioxide from the atmosphere and releases oxygen into the atmosphere, helping to maintain the planet's atmospheric stability. Disruption of this mechanism could exacerbate global warming by causing more carbon dioxide, a principal heat-trapping gas, to remain in the atmosphere.

Of the total pollution load entering the oceans worldwide, about three quarters comes from human activities on land including the release of industrial and municipal wastes, and farm runoff contaminated with pesticides and fertilizers. Shipping, accidental oil spills and ocean dumping account for 22 percent of ocean pollution.

Pollution from households causes major harm to oceans. What goes down the drain at home winds up in the sea: phosphate detergents, household solvents, and chemical cleaners flow into the oceans largely unnoticed. Sewage contributes about half the polluting nutrients that enter the oceans, damaging an ecosystem that only seems too vast to harm.

"The notion that the oceans are big enough to absorb these assaults may account for the lack of national and international policies to protect it," says Weber.

The coasts support some of the most vulnerable stages of ocean life, yet the coasts also draw people, whose very numbers pollute and physically destroy coastal terrain. Nine of the ten largest cities in the world, and half the world's population, are situated in coastal zones.

Coastal areas are also under assault from the $1.9 trillion travel and tourism industry. This industry, one of the world's fastest growing, has brought high densities of people into direct contact with wetlands, coral reefs, and other coastal habitats that replenish the oceans.

About one half of all national and international travelers are bound for coasts. A chief source of pollution, the tourism industry notices pollution most when it becomes pollution's victim. Each year, red tides, polluted beaches, and other environmental stresses erode hotel and travel profits.

Shrinking fish catches affect the food supply for many people, particularly those in developing countries.

"The economic effects of declining catches are now being felt throughout the global fishing industry," says Weber. In Canada, alone, some 50,000 people working in fishing and fish processing are out of work as a result of declining fish stocks and the closure of the depleted cod fishery to allow stocks to recover.

Governments are belatedly working together at the international level and are also taking steps at their own national levels to protect oceans. One such potentially effective step was initiated by the United Nations. The U.N. placed an international moratorium on highly destructive driftnet fishing, which, in 1990, ensnared and killed some 42 million seabirds, marine mammals, and other nontarget species. The moratorium went into effect on December 31, 1992, but some countries, such as Italy, France, and Taiwan, have ignored it and continue to use driftnets.

National governments need to eliminate policies that currently encourage overfishing. Abandoned Seas points out that globally over $124 billion is spent annually to catch $70 billion worth of fish. The $54 billion difference is largely government subsidies, which foster overfishing, Weber says. Eliminating these subsidies could simultaneously reduce taxpayer burdens and reduce overfishing.

"Governments may also have to consider restricting coastal development--or eventually banning it altogether in light of the threats of rising seas and stronger storms related to global warming," says the author.

The limited number of national initiatives to protect the oceans have had mixed results. Australia, for instance, made the entire 350,000 square kilometers of the Great Barrier Reef into a sanctuary in 1975 and placed it under a single park authority. Rather than closing the reef, the park authority manages it for multiple purposes in a manner designed to ensure the long-term viability of the entire ecosystem. The park authority, however, has been unable to control pollution from inland.

In the United States, efforts are underway to save the Chesapeake Bay, once one of the world's most productive estuaries. So far results are mixed. The Potomac River, one of the Bay's main tributaries, is cleaner and phosphorous levels in the Bay are down 20 percent. But polluted runoff from agriculture has increased, the population in the region continues to grow rapidly, development adjacent to the Bay continues, and the load of harmful nitrogen nutrients entering the Bay is on the rise.

The report emphasizes the need to integrate marine protection with the broader goals of sustainable development, such as reliable food supplies and clean water. Conversely, continued degradation of the oceans would be an impediment to economic progress and ecological stability.

"The complex links between land and sea may make the task of protecting the oceans seem daunting, if not impossible," says Weber. "But it is precisely because of these links--because the oceans touch the lives of all of us--that we cannot ignore the health of the oceans if we are to protect our own place on the planet."